This is a recurring topic on the mailing list. The answer, in short, is that :

each of the few persons actively involved with PHP-GTK has already far too much on her hands with the code base to also care for the site.

I could do it, as I am mostly a PHP-GTK user and not contributor, but this would have to be using Drupal, but... "heavy" frameworks are not compatible with the comparatively limited (wrt actual traffic served) server resources of php.net: if you checkout the source of the existing gtk.php.net site, you will notice if is extremely leightweight.

offloading the "notes" data from gtk.php.net to a non-php.net site like this one (php-gtk.eu) is not favorably considered by the powers that be, and would require some more code to be adapted on gtk.php.net anyway, leading back to 1.